MOOT & MUNGUIA: SEA URCHINS OF THE PHILIPPINES 
219 
The fact that there are so few endemics among the taxa occurring in more accessible, shallower 
waters strongly suggests that the vast majority of Philippine echinoid taxa from any depth will also 
be found to occur outside the region. 
This provides support for the idea that the Philippines is a center of overlap for many species 
ranges (Gaither and Rocha 2013). The center of overlap hypothesis suggests that the distinct fau¬ 
nas of the Pacific and Indian Oceans overlap in the Indo-Malay-Philippine biodiversity hotspot, 
which is bounded by the Philippines, Malay Peninsula, and New Guinea. For echinoids, the over¬ 
lap hypothesis is exemplified by the ranges of four echinoids that figured prominently during the 
shallow water component of the Hearst Expedition, and that typify the distributions of the major 
taxa to which they belong (Fig. 2). The species are characterized by relatively large, disparate 
ranges, but all have the Philippines as a common region of overlap. 
Echinoid highlights of the Expedition 
During approximately 35 days of collecting, the 2011 Hearst Philippine Biodiversity Expedi¬ 
tion found nearly as many echinoid species in the Verde Island Passage (VIP) region as have been 
recorded over the entire history of biodiversity work in the Red Sea. These findings are summa¬ 
rized in Figure 3, which shows bathymetry, by family, of all 52 of the species found during the 
Expedition. Although more species (about 65) have been recorded from the Philippine parts of the 
Sulu Sea and Archipelago, this region is vastly larger than the VIP. Present data indicate that the 
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Figure 3. Bathymetry of all 52 species collected during the 2011 Hearst Philippine Biodiversity Expedition. 
